More than one in 100 adult Americans are in jail or prison, an all-time high that is costing state governments nearly $50 billion a year, in addition to more than $5 billion spent by the federal government, according to a report released Thursday.

With more than 2.3 million people behind bars at the start of 2008, the United States leads the world in both the number and the percentage of residents it incarcerates, leaving even far more populous China a distant second, noted the report by the nonpartisan Pew Center on the States.

The ballooning prison population is largely the result of tougher state and federal sentencing imposed since the mid-1980s. Minorities have been hit particularly hard: One-ninth of black men age 20 to 34 are behind bars. For black women age 35 to 39, the figure is one in 100, compared with one in 355 white women in the same age group.

While studies generally find that imprisoning more offenders reduces crime, the effect is influenced by changes in the unemployment rate, wages, the ratio of police officers to residents, and the share of young people in the population.

In addition, when it comes to preventing repeat offenses by nonviolent criminals — who make up about half of the incarcerated population — alternative punishments such as community supervision and mandatory drug counseling that are far less expensive may prove just as or more effective than jail time.

Florida, which nearly doubled its prison population over the past 15 years, has experienced a smaller drop in crime than New York, which, after a brief increase, reduced its number of inmates to below the 1993 level.

“There is no question that putting violent and chronic offenders behind bars lowers the crime rate and provides punishment that is well deserved,” said Adam Gelb, director of the Pew Center’s Public Safety Performance Project and one of the study’s authors.

“On the other hand,” Gelb said, “there are large numbers of people behind bars who could be supervised in the community safely and effectively at a much lower cost — while also paying taxes, paying restitution to their victims and paying child support.”

Corrections spending climbs

About 91 percent of incarcerated adults are under state or local jurisdiction, and the report documents the tradeoffs state governments have faced as they have devoted ever larger shares of their budgets to house them. For instance, over the past two decades, state spending on corrections (adjusted for inflation) increased by 127 percent, while spending on higher education rose by 21 percent. For every dollar Virginia spends on higher education, it now spends about 60 cents on corrections. Maryland spends 74 cents on corrections per higher-education dollar.

Despite reaching its latest milestone, the nation’s incarcerated population has actually been growing far more slowly since 2000 than during the 1990s, when the spate of harsher sentencing laws began to take effect. These included a 1986 federal law mandating prison terms for crack-cocaine offenses that were up to eight times as long as for those involving powder cocaine. In the early 1990s, states across the nation adopted “three-strikes-you’re-out” laws and curtailed the discretion parole boards have in deciding when to release an inmate.

As a result, between 1990 and 2000, the prison population swelled by about 80 percent, increasing by as much as 86,000 per year.

By contrast, from 2007 to 2008, the prison population increased by 25,000 — a 2 percent rise.

Judges given more leeway

Meanwhile, the Supreme Court has issued decisions giving judges more leeway under mandatory sentencing laws, and a number of states, including Texas, are seeking to reduce their incarcerated population by adopting alternative punishments.

“Some of these (measures) would have been unthinkable five years ago,” noted Gelb. “But the bottom line is that states have to balance their budgets.”

“There is no question that putting violent and chronic offenders behind bars lowers the crime rate and provides punishment that is well deserved.”

In the past 20 years, according to the FBI, violent-crime rates fell by about 25 percent to 464 for every 100,000 people in 2007 from 612.5 in 1987.

Monetary cost of incarceration

It cost an average of $23,876 to imprison someone in 2005, the most recent year for which figures were available. But state spending varies widely, from $45,000 a year in Rhode Island to $13,000 in Louisiana.

About 91 percent of imprisoned adults are under state or local jurisdiction, and the report documents the trade-offs state governments have faced as they have devoted ever larger shares of their budgets to house them.

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